A plug connector of this kind is known in the art from FIG. 4 of German Patent Specification No. 35 25 568 A1. Herein, a connector engages by its connector tongue through a plug opening of the central row into the contact springs assigned to the plug opening. Cable wires are connected by pairs to the insulation displacement contacts assigned to the contact springs and arranged in the two outside rows of alterally extending clamping slots. With this arrangement contact tracks of the connector tongues must be assigned to specific cable wires of the cable wires connected by pairs. For this purpose, it is known in the art to provide the connector housing on its outside with an optical mark, in order to be capable to insert the connector always in the specific assignment to the cable wires connected by pairs.
However, the use of a connector housing with an optical mark requires that the user pay close attention when inserting the connectors into the bank. Faulty connections easily occur as the connectors can also be inserted reversed by 90.degree. into the bank disposed symmetrically to the longitudinal center axis. Corresponding disadvantages apply for multi-pole connectors, too. The connectors being, here, of relevance, are damping, cross, short-circuit and cord connectors of connection or test cords.